Butyric acid derivatives as novel photosensitizers

ABSTRACT

The invention relates to gamma -Hydroxy- gamma -phenyl- gamma benzoylbutyric acids, the esters and amides thereof, which are useful photosensitisers for the photopolymerisation of polymerisable compounds or compound mixtures including mixtures of unsaturated polyesters and copolymerisable monomeric compounds.

United States Patent 1 Rudolph et a1.

[ Oct. 21, 1975 BUTYRlC ACID DERIVATIVES AS NOVEL I PHOTOSENSITIZERS [75] Inventors: Hans Rudolph, Krefe'ld-Bockum;

Hans-Georg Heine; Karl Fuhr, both of Krefeld; Hermann. Schnell, Krefeld-Uerdingen, all of Germany [73] Assignee: Bayer Aktieng esellschaft, Germany [22] Fllfidi NOV-129, 1974 21 App1.No.: 528,098

Related US. Application Data [62] Division of Ser. No. 411,423, Oct. 31, 1973,

abandoned, which is a division of Ser. No. 867,939, 1

Oct. 20, 1969, Pat. No. 3,824,284.

30 Foreign Application Priority Data Nov. 6, 1.968 p Germany. 1807301- [56] References Cited UNITED STATES PATENTS 3,657,088 4/1'972 Heine et a1. 204/159.15 3,689,565 9/1972 Hoffman et a1 260/590 3,824,284 7/1974 Rudolph et a1. 260/559 R OTHER PUBLICATIONS Yokoyama et al., The Peracidoxidation of Ketones,

' 1V, Bu]. Chem. Soc. Japan, Vol. 138, No. 9, pp.

Primary ExaminerRichard B. Turer Attorney, Agent, or FirmConnol1y and Hutz [57] ABSTRACT The invention relates to 'y-Hydroxy-y-phenyLybenzoylbutyric acids, the esters and amides thereof, which are useful photosensitisers for the photopolymerisation of polymerisable compounds or compound mixtures including mixtures of unsaturated polyesters and copolymerisable monomeric compounds.

10 Claims, No Drawings -benzoin BUTYRIC ACID DERIVATIVES AS NOVEL PHOTOSENSITIZERS CROSS-REFERENCE TO RELATED APPLICATIONS in which R and R are identical or different and represent hydrogen, lower alkyl having 1 to about 4 carbon atoms, methoxy or halogen, R represents OI-I, OR, or optionally substituted NI-I and R represents lower alkyl having 1 to about 4 carbon atoms, and the lactones of formula Examples of such compounds are:

1,450,589), which are also benzoin derivatives, none has been able to find acceptance in industry. As the reasons for this, the inadequate storage stability in the dark and the excessively low reactivity of the polymerisable compounds mixed with such sensitisers, and at times also the discolouration of the polymers on prolonged storage in daylight, should be mentioned; furthermore, some of the compounds known as sensitisers are difficult-to obtain.

Against this, the compounds according to the invention are easily obtainable, reactive substances, mixtures of which with polymerisable compounds are storagestable for particularly long periods in the dark. The compounds according to the invention also behave satisfactorily as regards discolouration of the polymers in daylight. Because of their content of reactive groups they can also be easily built chemically into the compounds to be polymerised, for example into unsaturated polyesters.

When the compounds are used as photosensitisers they are appropriately employed in amounts of from about 0.1 to about 5 percent by weight, preferably of from about 0.5 to about 2.5 percent by weight, either by themselves or mixed with one another or mixed with photosensitisers of a different nature. Suitable polymerisable compounds are all substances of which the carbon-carbon double bonds are activated by, for exam ple, halogen atoms or carbonyl, cyanide, carboxyl, ester, amide, ether or aryl groups as well as carbon double bonds and carbon triple bonds. As examples there may be mentioned: styrene, vinyl toluene, divinyl benzene, vinyl acetate, vinyl chloride, vinylidene chloride, vinyl methyl ketone, acrylic and methacrylic acid, esters thereof such as the methyl, ethyl and allyl ester, their amides and nitriles, and other allyl esters, such as allyl acetate, phthalic acid diallyl ester and phosphoric acid triallyl ester, and mixtures of such compounds.

Moulding and coating compositions of mixtures, stabilised in the usual manner, of unsaturated polyesters and copolymerisable monomeric compounds can be used particularly advantageously, and unsaturated polyesters are here, as usual, to be understood as polycondensation products of a,B-unsaturated dicarboxylic acids such as, for example, maleic acid and fumaric acid, with polyols such as, for example, ethylene glycol -y-Hydroxy-'y-phenyl-7-benzoylbutyric acid, y-Hydroxy- -phenylbenzoylbutyric acid-'y-lactone y-l-lydroxy-y-phenyl-y-benzoylbutyric acid methyl ester a-(B-Carbonamido-ethyl )-benzoin a-(fiCarbonamido-ethyl )-4,4'-dimethylbenzoin a-(B-Carbonamido-ethyl)-4,4"dimethoxybenzoin a-(B-Carbonamido-ethyl)-4.4'-dichlorobenzoin and oe-[B-(N-Methoxymethyl )-carbonamido-ethyl] 2,722,512 and 2,488,828 and French Pat. No.

melting point l09-1 14 boiling point l-180 (0.2 mm Hg) melting point 74-77 melting point l52-l53 melting point l55156 melting point l48149 melting point l52-153 melting point 9899 and propanediol-l,2. A part of the unsaturated acids can be replaced by saturated acids, such as, for example, phthalic acid. Further modifications are possible through building-in monobasic acids and monohydric alcohols. So-called air-drying moulding compositions which in addition to the radicals of a,B-unsaturated dicarboxylic acids also contain [3,y-unsaturated ether radicals can also be employed, either as a constituent of the polyesters or as a constituent of further components of the mixture.

By copolymerisable monomeric compounds there are to be understood the unsaturated compounds which are usual in polyester technology, having vinyl groups which are optionally substituted in the a-position, or allyl groups which are optionally substituted in the ,8-position, preferably styrene.

The photopolymerisable compounds or mixtures can be stabilised by the addition of usual inhibitors, such as hydroquinone, in the known amounts. Polymerisation catalysts, for example peroxides, can optionally also be conjointly employed in the usual manner. In conjunction with the use of ketone hydroperoxide metal compounds, for example cobalt naphthenate, can be added for accelerating complete cure. In this case the storage stability of the photopolymerisable compositions is admittedly lowered. It is therefore advisable when manufacturing lacquer coatings to work in accordance with the so-called active primer method in which the coating composition is applied onto a peroxide-containing layer which has beforehand been applied to the substrate.

It is particularly advantageous to employ the new compounds in coating compositions to which paraffin or wax or wax-like substances are added which float to the surface at the start of the polymerisation and prevent the inhibiting action of atmospheric oxygen.

In order to protect light-sensitive substrates, for example light timbers, small amounts of customary ultraviolet absorbers may be added to the moulding and coating compositions without the reactivity being significantly impaired. Furthermore, small amounts of customary carriers and fillers as well as agents for conferring thixotropy, such as glass fibres, synthetic fibres,

silica and talcum, can be present during the photopolymerisation.

As radiation sources for carrying out the photopolymerisation, it is possible to use natural sun'- light or artificial radiation sources of which the emission lies in the range of about 250 to about 500 mu, preferably from about 300 to about 400 mp Mercury vapour lamps, xenon lamps or tungsten lamps are for example suitable. The compositions also rapidly cure to give colourless moulded and coated articles under the ultraviolet and visible radiation of low energy fluorescent lamps emitting rays of about 300 to about 580 mp..

When manufacturing mouldings from the sensitised compositions it proves particularly advantageous to be able to cure the compositions by appropriately metered irradiation without a significant heating effect, as a result of which larger mouldings can also be obtained free of cracks. In the absence of peroxides and metal accelerators the cure can also optionally be interrupted through placing the material in darkness and completed at any desired time after storing the prepolymers thus obtained.

The new compounds can be manufactured in a manner which is in itself known by addition of acrylic acid derivatives to benzoins and optionally further reaction of the adducts.

y-Hydroxy-'y-phenyl-y-benzoylbutyric acid can for example be obtained in accordance with the following instruction: 20 ml of acrylic acid ethyl ester and ml of 10% aqueous sodium hydroxide solution are added at C to a solution of 21.2 g of benzoin in 200 ml of tert.-butanol. Thereafter the reaction mixture is allowed to cool and diluted with a 5-fold amount of water, and unreacted benzoin is filtered off. The filtrate is carefully acidified and extracted with ether. After the usual working-up a crude product is obtained from which 23 g of crystals separate out after addition of benzene. After recrystallisation from ether/petroleum ether 8.5 g'of white crystals are obtained. Melting point 109 114C (cyclisation to give the lactone).

'y-Hydroxy-y-phenyl-y-benzoylbutyric acid-'y-lactone can for example be obtained in accordance with the following instruction: 43 g of acrylic acid ethyl ester and 50 ml of 10% aqueous sodium hydroxide solution are added to a solution of 25 g of benzoin in 200 ml of tert.-butanol at 70C. Thereafter the reaction solution is mixed with l l of water and cooled. The unreacted benzoin is filtered off and the alkaline filtrate is acidified. After the usual working-up 15.6 g of crude acid are obtained and are dissolved in benzene and filtered through silica gel. 9.3 g of oil lactone can be obtained in a pure form by distillation. Boiling point C 0.2 mm Hg); 1130 15895-15907.

a-(B-Carbonamido-ethyl)-benzoin can for example be obtained in accordance with the following instruction: a mixture of 12 g of acrylonitrile and 30 g of 10 potassium hydroxide solution is added at 60C to a solution of 42.5 g of benzoin in 600 g of tert.-butanol. Thereafter the mix is allowed to cool and -is introduced into 3 1 of ice water, and the precipitate which has separated out is filtered off and rinsed with water. After recrystallisation from ethyl acetate 25 g of a-(B-cabronamido-ethyl)-benzoin, melting point 152- 153C, are obtained.

The amide can however also for example be obtained in the following manner: a mixture of 7.1 g of acrylamide and 30 ml of 10% sodium hydroxide solution is added at 60C to a solution of 21.2 g of benzoin in 250 ml of tert.-butanol. Thereafter the mix is allowed to cool and is introduced into 3 liters of ice water, and the precipitate which has separated out is filtered off and rinsed with water. The precipitate is taken up in benzene and filtered through silica gel. Hereupon 13.5 g of unchanged benzoin and 7.3 g of the amide described above (melting point 152 153C) are obtained.

The methyl ester can for example be manufactured in the following manner: 3 g of the free acid are dissolved in 10 ml of ether, mixed with excess ethereal diazomethane solution and left to stand for 15 minutes at room temperature. After evaporation of the ether and recrystallisation of the residue from ether/petroleum ether, 1.7 g of 'y-hydroxy-y-phenyl-y-benzoylbutyric acid-methyl ester are obtained. Melting point 74- 77C.

EXAMPLE 1 10 g of extracted and freshly distilled acrylic acid methyl ester are mixed with 0.1 g of a-(B-carbonamido -ethyl )-benzoin.

The mixture is illuminated with a mercury vapour high pressure lamp (Philips l-IPK 125 W/L) through quartz glass in a waterbath at 24C, at a distance of 10 cm. The solution of the sensitiser in the monomer is at the same time contained in a quartz glass of internal diameterl .7 cm under a nitrogen atmosphere. The illumination time is 2% minutes. Immediately after illumination the quartz glass is introduced into an acetone/solid carbon dioxide mixture in order to prevent a thermal polymerisation. The solution of the polymer in the monomer and the solid polymer particles which are present on the inside of the quartz glasses on the side facing the mercury vapour high pressure lamp are transferred into a small round flask with the aid of small amounts of a solvent (methylene chloride).

Thereafter unpolymerised monomeric constituents and the solvent are distilled off in a rotating evaporator.

52- 53C) in toluene, as well as benzoin or photosensitisers according to the invention in equimolar amounts, are mixed into 100 parts by weight at a time of the form in which'the resin is supplied which has been described in example 2. The solutions thus obtained are applied to glass plates by means of afilm spreader (500 p.) and are illuminated with radiation from a fluorescent'lamp (Osram L 40W/70-l) at a distance of 5 cm.

Table 2 gives-the times for the paraffin to float to the After drying in vacuo to constant weight at 60C, the 10 Surface and the times until a pencil hardness 6 H is quantity of polymer amounts to 12.8 percent by weight. eached.

TABLE 2 Additive Time for Pencil hardin parts paraffin. ness 6 H, by weight to float I after minutes Sensitiser relative to surto form face, in which after resin is minutes supplied Benzoin 1.06 4.9 20.0 y-Hydroxy-y-phenyl-yhenzoylbutyric acid 1142 1.9 16.0 'y-Hydroxy-y-phenyl-y-benzoylbutyric acid methyl ester 1.49 2.6 19.0 a-(B-Carhonamido-ethylJ- benzoin 1.42 1.9 16.0

If the sensitiser is absent, the quantity of polymer is less than 0.1

EXAMPLE 2 An unsaturated polyester manufactured by condensing 152 parts by weight of maleic anhydride, 141 parts by weight of phthalic anhydride and 195 parts by weight of propanediol-l,2 is mixed with 0.045 parts by weight of hydroquinone and dissolved in styrene to give a 65 percent by weight solution.

2 parts by weight of two different known photosensitisers on the one hand of three different photosensitisers according to the invention on the other hand are added to 100 parts by weight at a time ofthis form in which the resin is supplied, and the mixtures are stored at 60C, with exclusion of light, until they gel. Table 1 gives the sensitisers and the storage stability values at 60C.

TABLE 1 Storage stability in the dark of the form in which a typical polyester resin is supplied, with the addition of 2 parts by weight of sensitiser.

Storage Stability Sensitiser at 60C Benzoin less than 1 day Benzoin ethyl ether less than 1 day more than 10 days more than 10 days EXAMPLE 3 parts by weight of styrene, 1 part by weight of a I 10 percent by weight solution of paraffin (melting point We claim:

1. In the process of preparing coatings and molded bodies by photopolymerizing a mixture of at least one ethylenically unsaturated polymerizable compound and a photosensitizer by irradiating said mixture with a radiation source, the improvement which comprises employing 0.1 to 5% by weight, based on said ethylenically unsaturated compound, of a photosensitizer of the formula ii C-C-CH -CH C0R, R, g

wherein R, and R are identical or different and selected from the group consisting of hydrogen, alkyl having 1 to 4 carbon atoms, methoxy and halogen and R is alkyl having 1 to 4 carbon atoms.

2. The process of claim 1 wherein the photosensitizer is employed in an amount of 0.5 to 2.5% by weight based on the ethylenically unsaturated compound.

3. The process of claim 1 wherein each of R and R is hydrogen and R is methyl.

4. The process of claim 1 wherein said at least one ethylenically unsaturated compound is a mixture of an unsaturated polyester which is the condensation product of an a,B-dicarboxylic acid and a polyol and an ethylenically unsaturated copolymerizable monomer.

5. The process of claim 1 wherein each ethylenically unsaturated compound is selected from the group consisting of styrene, vinyl toluene, divinylbenzene, vinyl acetate, vinyl chloride, vinylidene chloride, vinyl methyl ketone, acrylic acid, methacrylic acid, acrylic acid methyl ester, methacrylic acid methyl ester, acrylic acid ethyl ester, methacrylic acid ethyl ester,

wherein R and R are identical or different and selected from the group consisting of hydrogen, alkyl having 1 to 4 carbon atoms, methoxy and halogen and R is alkyl having 1 to 4 carbon atoms.

7. The composition of claim 6 wherein the photosensitizer is employed in an amount of 0.5 to 2.5% by weight based on the ethylenically unsaturated compound.

8. The composition of claim 6 wherein each of R and R is hydrogen and R is methyl.

9. The composition of claim 6 wherein said at least one ethylenically unsaturated compound is a mixture of an unsaturated polyester which is the condensation product of an a,fi-dicarboxylic acid and a polyol and an ethylenically unsaturated copolymerizable monomer.

10. The composition of claim 6 wherein each ethylenically unsaturated compound is selected from the group consisting of styrene, vinyl toluene, divinyl benzene, vinyl acetate, vinyl chloride, vinylidene chloride, vinyl methyl ketone, acrylic acid, methacrylic acid, acrylic acid methyl ester, methacrylic acid methyl ester, acrylic acid ethyl ester, methacrylic acid ethyl ester, acrylic acid allyl ester, methacrylic acid allyl ester, acrylic acid amide, methacrylic acid amide, acrylic acid nitrile, methacrylic acid nitrile, allyl acetate, phthalic acid diallyl ester, phosphoric acid triallyl ester and mixtures thereof. 

1. IN THE PROCESS OF PREPARING COATINGS AND MOLDED BODIES BY PHOTOPOLYMERIZING A MIXTURE OF AT LEAST ONE ETHYLENICALLY UNSATURATED POLYMERIZABLE COMPOUND AND A PHOTOSENSITIZER BY IRRADIATING SAID MIXTURE WITH A RADIATION SOURCE, THE IMPROVEMENT WHICH COMPRISES EMPLOYING 0.1 TO 5% BY WEIGHT, BASED ON SAID ETHYLENICALLY UNSATURATED COMPOUND, OF A PHOTOSENSITIZER OF THE FORMULA
 2. The process of claim 1 wherein the photosensitizer is employed in an amount of 0.5 to 2.5% by weight based on the ethylenically unsaturated compound.
 3. The process of claim 1 wherein each of R1 and R2 is hydrogen and R4 is methyl.
 4. The process of claim 1 wherein said at least one ethylenically unsaturated compound is a mixture of an unsaturated polyester which is the condensation product of an Alpha , Beta -dicarboxylic acid and a polyol and an ethylenically unsaturated copolymerizable monomer.
 5. The process of claim 1 wherein each ethylenically unsaturated compound is selected from the group consisting of styrene, vinyl toluene, divinylbenzene, vinyl acetate, vinyl chloride, vinylidene chloride, vinyl methyl ketone, acrylic acid, methacrylic acid, acrylic acid methyl ester, methacrylic acid methyl ester, acrylic acid ethyl ester, methacrylic acid ethyl ester, acrylic acid allyl ester, methacrylic acid allyl ester, acrylic acid amide, methacrylic acid amide, acrylic acid nitrile, methacrylic acid nitrile, allyl acetate, phthalic acid diallyl ester, phosphoric acid triallyl ester and mixtures thereof.
 6. A mixture of at least one ethylenically unsaturated polymerizable compound and from 0.1 to 5% by weight, based on said ethylenically unsaturated compound of a photosensitizer of the formula
 7. The composition of claim 6 wherein the photosensitizer is employed in an amount of 0.5 to 2.5% by weight based on the ethylenically unsaturated compound.
 8. The composition of claim 6 wherein each of R1 and R2 is hydrogen and R4 is methyl.
 9. The composition of claim 6 wherein said at least one ethylenically unsaturated compound is a mixture of an unsaturated polyester which is the condensation product of an Alpha , Beta -dicarboxylic acid and a polyol and an ethylenically unsaturated copolymerizable monomer.
 10. The composition of claim 6 wherein each ethylenically unsaturated compound is selected from the group consisting of styrene, vinyl toluene, divinyl benzene, vinyl acetate, vinyl chloride, vinylidene chloride, vinyl methyl ketone, acrylic acid, methacrylic acid, acrylic acid methyl ester, methacrylic acid methyl ester, acrylic acid ethyl ester, methacrylic acid ethyl ester, acrylic acid allyl ester, methacrylic acid allyl ester, acrylic acid amide, methacrylic acid amide, acrylic acid nitrile, methacrylic acid nitrile, allyl acetate, phthalic acid diallyl ester, phosphoric acid triallyl ester and mixtures thereof. 